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Permafrost plagues Alcan as historic highway celebrates 70th birthday

The New York Times reports that the Alcan – the Alaska Canada military highway that links Alaska to the Lower 48 – is facing challenges unforeseen when it was built 70 years ago.

The highway is considered one of the greatest engineering feats of the 20th century. Built in just eight months, the Army Corps of Engineers battled bugs, extreme weather, and unforgiving terrain to build a supply road that snaked through Canada up to Alaska on President Roosevelt’s orders. The president worried that the invading Japanese would occupy the territory and head toward the U.S. mainland if Alaska wasn’t linked up with the rest of the nation.

The pioneer road was opened the following October, and what started out as a treacherous gravel road passable by only military vehicles is now a “very good standard two-lane highway,” Wally Hidinger, who directs transportation engineering for the Yukon territorial government, told the New York Times.

But the highway is facing problems that could not have been predicted when the highway was carved out of the landscape in 1942. The issue is permafrost – ground that remains permanently frozen – that is now melting, leaving pavement cracked and unstable. The permafrost is melting for several reasons, including climate change. High northern latitudes are changing faster than lower latitudes, and permafrost can be expected to melt faster in future years.

Wildfires also change the surface of the road, and can lead to melting of the permafrost beneath. Improvements to the road like heat-absorbing pavement also play a role in melting the ground beneath the road. But even simple measures, such as ripping up vegetation on the side of roads and exposing the dark soil, can contribute to melting permafrost, and in turn, cracked roads.

Compounding the problem is the fact that engineers aren’t sure where exactly the permafrost patches are. They are using ground-penetrating radar and instruments to stake out the location of permafrost areas. Elsewhere on the highway, light-colored pavement has been installed to ease the melting. But that pavement costs 10 times as much.